1. Field of Invention
This invention relates to a power-saving device and, in particular, to a device for interrupting the power supply to a computer monitor when the computer is not being used.
2. Brief Statement of the Prior Art
The concern for efficient utilization of resources, in particular, attempts to avoid unnecessary power consumption, have focused recently on the substantial amount of electrical power consumed by computers. The fastest expanding use of electrical energy is in office equipment and personal computers represent approximately 5-10% of the annual power consumption office equipment. Advances have been made in controlling the power supply to the central processing unit of computers. These various control circuits have been applied to save battery power in portable computers. The typical office computer, however, utilizes a cathode ray tube (CRT) monitor which is usually powered independently of the power supply to the central computer unit. Heretofore, no attempt has been made to provide a control device which will interrupt the power supply to a computer monitor during periods of inactivity of the computer. Since a typical CRT monitor has a power consumption of about 100 watts, the monitors represent approximately 40-60% of the total power consumption of an office computer. It has been estimated that a computer monitor is only in use approximately 20% of the time that it receives power. Despite the high power consumption by CRT monitors, prior efforts to control power to computers have not addressed the power consumed by these monitors.
There are also software products which are intended to prevent "burn-out" of CRT monitors which results when the screen display on a monitor is unchanged for prolonged periods of time. These products blank the screen, or cause display of changing images. The software does not, however, conserve energy as most of these products result in approximately 20% more energy consumption than a blank screen on the monitor.
Various attempts have been made to interrupt the power supply to computers and related instruments. U.S. Pat. No. 4,665,536 discloses a power interruption unit for a workstation. While this device is suitable for workstation applications, it is not useful for most computer systems as its operation results in a complete loss of data in memory at the workstation. Additionally, since the workstations of various manufacturers have different operating systems, this device must be programmed individually for each manufacturer's workstation product, typically by specialized driver software. Thus, the unit is not universally applicable.
U.S. Pat. Nos. 4,419,917 and 4,463,646 disclose power-saving devices for use with electronic musical instruments such as electronic organs and pianos. U.S. Pat. No. 4,417,135 discloses a power-saving device for a tape recorder. U.S. Pat. No. 4,698,748 discloses a device which provides a sleep control for a computerized automotive control system. U.S. Pat. No. 4,825,143 discloses a power-saving device for use with a multimeter to deactivate its digital display and extend the battery life. U.S. Pat. No. 4,780,843 discloses a power control to the sub-system of a complex data processing system. U.S. Pat. No. 4,455,623 discloses a control to save battery power by reducing the power drain of a microprocessor of a portable computer. U.S. Pat. No. 4,667,289 discloses a power control unit which shuts off power to independently powered peripheral devices when the computer is shut off. U.S. Pat. No. 5,182,810 discloses a low power standby control for a microprocessor used in a battery powered portable computer.
Heretofore, there has been no control system devised specifically for controlling the power to a CRT monitor which will interrupt the electrical power supply to the monitor during periods of inactivity of the computer.